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COMPTEST 2003 Chalons en Champagne G. Nicoletto & E. Riva Boundary conditions on RV Post, Han and Ifju (1994) Carvelli & Poggi (2001) where u(x) is the displacement field in the RV u 0 is a rigid displacement of the RV is a small rigid rotation of RV E is the average strain (macroscopic) of RV ũ(x) is a periodic displacement associated to microscopic strain field within RV Free surface

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Stresses and Damage COMPTEST 2003 Chalons en Champagne G. Nicoletto & E. Riva a b c d Step a The critical stress is perpendicular to the fill yarn surface. The wedge elements of the straight portion of the fill yarns fail first. Initial damage occurs near the fill yarns. The critical stress is representative of damage initiation in the matrix.

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COMPTEST 2003 Chalons en Champagne G. Nicoletto & E. Riva a b c d Step b The critical stress direction does not change. It is perpendicular to the fill yarn surface. Damage continues in the fill yarns. Damage now involves the brick elements next to the wedge elements. The damage spreads into the matrix. Stresses and Damage

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COMPTEST 2003 Chalons en Champagne G. Nicoletto & E. Riva a b c d Step c The wedge elements, where the two perpendicular yarns are close to each other, fail. Fiber failure occurs in the fill yarn. Failure occurs where the yarn is curved to the maximum. Stresses and Damage

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COMPTEST 2003 Chalons en Champagne G. Nicoletto & E. Riva a b c d Step d Failure extends to the neighboring brick elements up to final catastrophic collapse. In this final stage different failure modes are activated such as transverse and longitudinal shear, and transverse direct stress. Stresses and Damage

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Conclusions COMPTEST 2003 Chalons en Champagne G. Nicoletto & E. Riva Optical inspection of a twill-weave laminate during tensile testing showed different damage mechanisms. Finite element modelling of an appropriate RV provided the macroscopic stress-strain relation of a woven laminate that were compared to experimental results. The finite element model of the RV provided the microscopic stresses and strains within matrix and reinforcements. An iterative procedure based on a damage routine has been developed to simulate damage evolution. A first correlation between experimental observations and computed damage evolution in a twill-weave laminate is encouraging.